The present invention relates to an operating state detecting method for internal combustion engines for determining whether an internal combustion engine is being accelerated and/or whether it is being decelerated, and an operating state detecting apparatus for implementing this detecting method.
In controlling an internal combustion engine, it is often necessary to determine whether the engine is being accelerated or decelerated. For instance, where an electronic fuel injection (EFI) device is used for feeding fuel to an internal combustion engine, it is determined whether the engine is being accelerated or decelerated, and the finding is taken into consideration in determining the quantity of fuel to be injected.
The EFI device is comprised of an electromagnetic fuel injection valve (injector) for injecting fuel into an air intake pipe or a cylinder of the engine, a fuel pump for feeding fuel to the injector, a pressure regulator for keeping the pressure of fuel fed to the injector substantially constant, and an electronic control unit (ECU) for controlling the injector so that it may inject a predetermined quantity of fuel when the internal combustion engine is at a predetermined position of rotational angle.
The ECU, provided with injection quantity operating means for arithmetically operating the fuel injection quantity on the basis of various control conditions such as the atmospheric pressure and the engine temperature and a drive circuit for supplying a drive signal to the injector so that the injector injects the arithmetically operated quantity of fuel, controls the injector so that a mixture in a predetermined air/fuel ratio is supplied into each cylinder of the engine according to various control conditions.
In order to determine the quantity of fuel to be injected by the injector, a fuel injection device of this kind needs knowledge of the quantity of air having flowed into each cylinder of the engine. One of known ways to determine the quantity of air having flowed into each cylinder is to estimate it from the (negative) pressure in the air intake pipe and the volume efficiency of the engine.
In an internal combustion engine wherein the fuel injection quantity is determined on the basis of the estimated quantity of air having flowed into each cylinder from the pressure in the air intake pipe and the volume efficiency of the engine, when the engine is being accelerated or decelerated, the air/fuel ratio of the mixture may be made leaner or richer by a delay in response. Thus, when a driver abruptly opens a throttle valve to accelerate the engine, since a delay is occurred by the time that the estimated quantity of air flowing into each cylinder is corrected by means of detecting a pressure variation in the air intake pipe ensuring from the variation in the opening degree of the throttle valve, the quantity of fuel injection arithmetically operated by the ECU tends to be smaller than the quantity of injection actually required by the engine and accordingly the air/fuel mixture becomes too lean. Meanwhile, when the driver abruptly closes the throttle valve to decelerate the engine, a similar delay in response makes the quantity of air/fuel mixture arithmetically operated by the ECU tends to be greater than the quantity of air/fuel mixture actually required by the engine and accordingly the air/fuel mixture becomes too rich. For this reason, if the quantity of fuel injection is controlled with no allowance for the delay in response at the time of accelerating or decelerating the engine, the exhaust gas composition may deteriorate, and so may deteriorate the operating performance of the engine, at the time of accelerating or decelerating the engine.
In order to solve the problem noted above, an electronic fuel injection device may be provided with means for detecting an accelerating state and a decelerating state of an engine and, when either of these states is detected, prevent the exhaust gas composition or the operating performance of the engine from deteriorating at the time of acceleration or deceleration by correcting the quantity of fuel injection arithmetically operated on the basis of the estimated quantity of air flowing into each cylinder and thereby keeping the air/fuel ratio within an appropriate range.
Control taking into account the states of acceleration or deceleration of an engine may be carried out not only when the quantity of fuel injection into the engine is to be controlled but also when, for instance, the ignition timing of the engine is to be controlled to improve the accelerating performance or the exhaust composition of the engine.
A fuel injection device according to the prior art comprises a throttle position sensor to detect the opening degree of the throttle valve. The fuel injection device determines that the engine is being accelerated when the variation of the opening degree of the throttle valve by a predetermined quantity in the accelerating direction in a predetermined length of time is detected and determines that the engine is being decelerated when the variation of the opening degree of the throttle valve by a predetermined quantity in the decelerating direction in a predetermined length of time is detected.
Since the internal combustion engine according to the prior art detects the accelerating state or the deteriorating state of the engine from any variation in the opening degree of the throttle as described above, it requires a throttle position sensor and inevitably a corresponding increase in cost.
An object of the present invention is to provide an operating state detecting method and apparatus for internal combustion engines whereby it can be determined, without a throttle position sensor, whether an internal combustion engine is being accelerated and/or whether it is being decelerated from any variation in pressure within an air intake pipe.
The present invention provides an operating state detecting method for internal combustion engines for determining whether an internal combustion engine is being accelerated or decelerated. According to the present invention, a plurality of rotational angle positions of a crankshaft of an internal combustion engine are predetermined in advance to be sampling positions for sampling pressures within the air intake pipe of the internal combustion engine, and each pressure within the air intake pipe of the internal combustion engine sampled at each sampling position is stored. Every time each pressure within the air intake pipe is sampled at each sampling position, a newly sampled pressure within the air intake pipe is compared with a previous pressure within the air intake pipe sampled at the same sampling position one combustion cycle before, and whether the internal combustion engine is in an accelerating state and/or whether it is in a decelerating state is determined from the result of comparison.
In one aspect of the invention, the newly sampled pressure within the air intake pipe is compared with the previous pressure within the air intake pipe obtained by sampling at the same sampling position one combustion cycle before, and it is determined that the internal combustion engine is being accelerated when the newly sampled pressure within the air intake pipe is higher by at least a predetermined level than the previously sampled pressure within the air intake pipe and that the internal combustion engine is being decelerated when the newly sampled pressure within the air intake pipe is lower by at least a predetermined level than the previously sampled pressure within the air intake pipe.
As described above, if it is so disposed that the internal combustion engine be determined whether in an accelerating state and/or whether in a decelerating state by specifying in advance a plurality of rotational angle positions of the crankshaft of the internal combustion engine to be sampling positions for sampling the pressure within the air intake pipe of the internal combustion engine and, every time the pressure within the air intake pipe is sampled at a sampling position, comparing the newly sampled pressure within the air intake pipe with the previous pressure within the air intake pipe obtained by sampling at the same sampling position one combustion cycle before, whether the engine is in an accelerating state and/or whether it is in a decelerating state can be detected without having to use a throttle position sensor, which makes possible a reduction in cost.
In determining an accelerating state or a decelerating state from the pressure within the air intake pipe, it is conceivable to compare the pressure within the air intake pipe detected at each sampling position with a predetermined reference level. Since the pressure within the air intake pipe significantly pulsates as the engine proceeds from one stroke to another, it is impossible to accurately detect the accelerating state or the decelerating state by comparing the pressure within the air intake pipe detected at each sampling position with a predetermined reference level. It is also conceivable to eliminate the impact of the pulsation of the pressure within the air intake pipe by integrating pressures within the air intake pipe for one combustion cycle, comparing the result of integration with a predetermined reference level, but by this method the accelerating state or the decelerating state at each rotational angle position of the engine cannot be detected without waiting a full combustion cycle, it is impossible to control the engine on a real time basis according to its operating state at every moment.
On the contrary, if a newly detected (current) pressure within the air intake pipe is compared with the pressure within the air intake pipe one combustion cycle before as described above, it is possible to clearly detect the accelerating state or the decelerating state at every moment without delay even where the pressure within the air intake pipe pulsates significantly as the engine proceeds from one stroke to another.
The invention is applicable to both mono-cylinder internal combustion engines and multi-cylinder internal combustion engines. Where each cylinder of a multi-cylinder internal combustion engine is provided with an air intake pipe, the pressure of any one air intake pipe can be sampled.
In the case that the invention is applied to an internal combustion engine of which one air intake pipe provided with a throttle valve is connected via a surge tank to the air intake ports of a plurality of cylinders, the pressure within the air intake pipe may as well be indirectly detected by sampling the pressure in the surge tank. Although the pulsation of the pressure in the surge tank due to stroke changes of the engine is relatively small, it is not possible to completely eliminate the impact of the pulsation arising from stroke changes of the engine. Therefore, it is useful, even where the pressure within the air intake pipe is to be detected from the pressure in the surge tank, to compare the pressure within the air intake pipe detected at each sampling position with the pressure within the air intake pipe sampled one combustion cycle before as described in the present invention.
Thus, the method according to the invention is useful for multiple purposes because it is applicable to both cases where the pressure within the air intake pipe is to be directly detected and cases where it is to be indirectly detected by way of the pressure within a surge tank.
Thus, an operating state detecting apparatus for internal combustion engines to be used for implementing the detecting method described above comprises a pressure sensor for detecting pressures within an air intake pipe of an internal combustion engine, a rotational angle sensor for generating a rotational angle detection signal for detecting each of the plurality of rotational angle positions of a crankshaft of the internal combustion engine, a pulse generator for generating a reference pulse for detecting a reference rotational angle position of the crankshaft of the internal combustion engine, air intake pipe internal pressure sampling means for sampling, at each of the plurality of rotational angle positions detected from the rotational angle detection signal as sampling positions, the pressure within the air intake pipe detected by the pressure sensor at each sampling position, storage means for identifying the sampling positions with reference to the reference rotational angle position detected by the reference pulses and storing the pressures within the air intake pipe sampled at different sampling positions, and comparative determination means for comparing the pressures within the air intake pipe newly sampled at each sampling position with the pressure within the air intake pipe sampled at the same sampling position one combustion cycle before and stored by the storage means, determining that the internal combustion engine is being accelerated when the newly sampled pressure within the air intake pipe is higher by at least a predetermined level than the previously sampled pressure within the air intake pipe, and determining that the internal combustion engine is being decelerated when the newly sampled pressure within the air intake pipe is lower by at least a predetermined level than the previously sampled pressure within the air intake pipe.
As the rotational angle sensor mentioned above, a power generating coil provided in a multi-polar magnet generator driven by the internal combustion engine and supplying A.C. voltages of a plurality of cycle while the crankshaft of the internal combustion engine completes one revolution can be used. In this case, the air intake pipe internal pressure sampling means is so comprised as to use as the sampling position at least either of a rotational angle position of the crankshaft matching each zero cross point of the A.C. voltages supplied by the power generating coil and a rotational angle position of the crankshaft matching each peak point of the A.C. voltages.
Since the use of the power generating coil in the magnet generator fitted to the internal combustion engine as the rotational angle sensor as described above eliminates the need to provide a rotational angle sensor specially for the purpose, the invention can be implemented without complicating the construction of the internal combustion engine or inviting an increase in cost.
Also as the rotational angle sensor, a signal generating device (encoder) for generating a pulse signal every time the internal combustion engine rotates by a predetermined angle can be used. In this case, the air intake pipe internal pressure sampling means is so comprised as to use as the sampling position at least either of a rotational angle position of the crankshaft matching a leading edge of the pulse signal generated by the signal generating device and a rotational angle position of the crankshaft matching a trailing edge of the pulse signal.
While each of the constructions described above uses a rotational angle sensor for generating rotational angle signals for determining the sampling positions of the pressure within the air intake pipe and a pulse generator for generating reference pulses, it is also possible to use a rotational angle sensor (encoder) for generating both rotational angle detection pulses for determining sampling positions and reference pulses. In this case, the rotational angle detection pulses and the reference pulses can be distinguished from each other by, for instance, differentiating them in pulse width.
The rotational angle detection pulses and the reference pulses can also be distinguished from each other by having the pulses generated at equal angular intervals recognized as rotational angle detection pulses and the pulses generated at unequal angular intervals recognized as reference pulses, while a series of pulses equal in pulse width, each being generated every time the internal combustion engine rotates by a predetermined minute angle, generates partly at unequal intervals.